Fusion peptides of CD4 helper T cell epitopes and vaccines thereof

ABSTRACT

Disclosed are a fusion peptide of CD4 helper T cell epitopes, a nucleic acid encoding the same and an immunogenic composition comprising the same. The epitope fusion peptide comprises a cytomegalovirus epitope and an influenza virus epitope. The epitope fusion peptide can substantially improve the level of cellular immune response to a target immunogen, particularly a weak immunogen, and is an effective means for overcoming the immune tolerance of immune system to an antigen, particularly to a tumor antigen or an infection-related antigen, and is suitable for efficiently enhancing the efficacy of vaccine.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/CN2017/104401, filed Sep. 29, 2017, the disclosure of which is incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention belongs to the fields of molecular biology and immunology. In particular, the present invention relates to a fusion peptide of CD4 helper T cell epitopes, especially to a vaccine comprising the epitope fusion peptide, and use thereof.

BACKGROUND ART

T helper cells (Th cells) are the cells that play an important role in the immune system, particularly in the adaptive immune system. They promote the activities of other immune cells by releasing T cell cytokines. These cells help to inhibit or modulate immune responses. They are essential in the conversion of B cell antibody classes, the activation and growth of cytotoxic T cells, and the maximization of bactericidal activity of phagocytic cells, such as macrophages.

Mature Th cells expressing the protein CD4 are known as CD4⁺ T cells. As helper T cells, such CD4⁺ T cells are typically subjected to a pre-defined process within the immune system. For example, when antigen presenting cells express an antigen on MHC class II, CD4⁺ cells would assist these cells by a combination of cell-to-cell interactions (e.g., CD40 (protein) and CD40L) and cytokines.

The importance of helper T cells can be seen with respect to HIV, a virus that primarily infects CD4⁺ T cells. In the late stage of HIV infection, loss of functional CD4⁺ T cells leads to a stage of infectious symptoms known as acquired immune deficiency syndrome (AIDS). When HIV virus is found early in blood or other body fluids, a continuous treatment may delay its occurrence. If AIDS occurs, the treatment can also better manage the course of AIDS. Other rare diseases, such as lymphopenia, result in loss or dysfunction of CD4⁺ T cells. These diseases produce similar symptoms, many of which are fatal.

Antigenic epitope, “epitope” for short, also known as “antigenic determinant”, refers to chemical groups on the surface of an antigen that determines the antigen specificity. An antigenic epitope can be recognized by the immune system, especially by antibodies, B cells or cells. A site of an antibody capable of recognizing an antigenic epitope is referred to as a “paratope” or an “antibody determinant”. Although an antigenic epitope usually refers to a part of foreign protein or the like, an epitope that can be recognized by the autoimmune system is also classified as an antigenic epitope.

The epitopes of protein antigen are divided into conformational epitopes and linear epitopes according to their structures and interactions with a paratope. Since a conformational epitope consists of discrete portions in the amino acid sequence of an antigen, the interaction of a paratope with the antigenic epitope is based on the three-dimensional characteristics and shape of the surface or tertiary structure of the antigen. Most antigenic epitopes belong to conformational epitopes. In contrast, a linear epitope consists of a continuous amino acid sequence of an antigen, and the interaction with the antigen is based on its primary structure.

A T cell epitope consists mainly of a short peptide of 8-17 amino acids and exists on antigen-presenting cells (APC), which as an antigen epitope would bind to major histocompatibility complex (MHC) to form a complex and bind to the corresponding T cell epitope receptors, thereby activating T cells and generating a corresponding cellular immune response (Shimonikevitz et al., 1984; Babbitt et al., 1985; Buus et al., 1986; Townsend and Bodmer, 1989). There are two major classes of MHC molecules which bind to an epitope. Among them, major histocompatibility complex class I usually presents a T cell antigenic epitope consisting of a polypeptide of 8 to 11 amino acids in length, while major histocompatibility complex class 11 presents a relatively longer I cell antigenic epitope consisting of 13-1.7 amino acids.

Among T cell epitopes, helper T cell epitopes (Th epitopes) refer to a class of T cell epitopes which bind to MHC molecules and form complexes that can be recognized by CD4 helper T cell receptors. Th epitopes bind primarily to the molecules present on the surfaces of antigen-presenting cells (APC) encoded by MHC class II genes. The complexes of class II molecule and peptide epitope are then recognized by the specific T cell receptors (TCR) on the surfaces of T helper lymphocytes. In this way, the T cells presenting an antigenic epitope in the context of MHC molecules can be activated and provide the essential signal for B lymphocyte differentiation. Traditionally, the source of T-helper epitope of peptide immunogen has been a carrier protein covalently coupled to a peptide, but the coupling process may involve other issues, such as modification of antigenic determinants during the coupling process and induction of an antibody against the carrier at the expense of an antibody against the peptide (Schutze, M. P., Leclerc, C. Jolivet, M. Audibert, F. Chedid, L. Carrier-induced epitopic suppression, a major issue for future synthetic vaccines. J Immunol. 1985, 135, 2319-2322; DiJohn, D., Torrese, J. R. Murillo, J. Herrington, D. A. et al. Effect of priming with carrier on response to conjugate vaccine. The Lancet. 1989, 2, 1415-1416). In addition, the use of an irrelevant protein in the preparation may involve quality control problems. The choice of a suitable carrier protein, which is important in the design of peptide vaccine, is limited by the factors, such as toxicity and feasibility in a large-scale production. There are other limitations to this method, including the load size of peptide that can be coupled and the dose of carrier that can be safely administered (Audibert, F. a. C., L. 1984. Modern approaches to vaccines. Molecular and chemical basis of virus virulence and immunogenicity., Cold Spring Harbor Laboratory, New York.). Although carrier molecules allow to induce a strong immune response, they are also associated with the adverse effects, such as inhibition of anti-peptide antibody response (Herzenberg, L. A. and Tokuhisa, T. 1980. Carrier-priming leads to hapten-specific suppression. Nature 285: 664; Schutze, M. P., Leclerc, C., Jolivet, M. Audibert, F., and Chedid, L. 1985. Carrier-induced epitopic suppression, a major issue for future synthetic vaccines. J Immunol 135: 2319; Edinger, H. M., Felix, A. M., Gillessen, D., Heimer, E. P., Just, M., Pink, J. R., Sinigaglia, F., Sturchler, D., Takacs, B., Trzeciak, A., and et al., 1988. Assessment in humans of a synthetic peptide-based vaccine against the sporozoite stage of the human malaria parasite, Plasmodium falciparum. J Immunol 140: 626).

In general, an immunogen must contain a helper T cell epitope in addition to an epitope to be recognized by a surface Ig or the receptors present on the cytotoxic T cells. It will be appreciated that these types of epitopes may be very different. For B-cell epitopes, the conformation is important because B-cell receptors bind directly to native immunogens. In contrast, an epitope to be recognized by T cells is independent of the conformational integrity of the epitope, and consists of a short sequence of about 9 amino acids against CTL and a slightly longer sequence (having less length restriction) against helper T cells. The only requirement for these epitopes is that they can be accommodated in the binding clefts of class I or class II molecules, respectively, and the complexes can then bind to T cell receptors. The binding sites of class II molecules are open at both ends, allowing a greater variation in the length of a peptide (Brown, J. H., T. S. Jardetzky, J. C. Gorga, L. J. Stern, R. G. Urban, J. L. Strominger and D. C. Wiley. 1993. Three-dimensional structure of the human class II histocompatibility antigen HLA-DR1. Nature 364: 33) that binds to a reported epitope of as short as 8 amino acid residues (Fahrer, A. M., Geysen, H. M., White, D. O., Jackson, D. C. and Brown, L. E. Analysis of the requirements for class IT-restricted T-cell recognition of a single determinant reveals considerable diversity in the T-cell response and degeneracy of peptide binding to HEd J. Immunol. 1995. 155: 2849-2857).

A Th epitope can stimulate and activate helper ‘I’ cells, and accordingly promote activation of CD8 T cells and B cells, ultimately increasing the immune response. In essence, a Th epitope, in addition to being able to activate an immune response against itself, is also effective in aiding the immune response to other antigens or epitopes associated therewith. Thus, a heterologous strong Th epitope can be fused to a target immunogen, thereby increasing the immunogenicity of the target immunogen. An artificial strong Th epitope called PADRE (pan HLA DR-binding Epitope) has been used in the fusion construction of multiple vaccines to increase the levels of immune responses to the relevant immunogens (del Guercio et al., Vaccine, 1997, 15: 441.; Franke, E. D. et al., Vaccine, 1999, 17:1201; Jeff Alexander et al., J Immunol, 2000, 164 (3) 1625-1633; Jeff Alexander et al., Vaccine, 2004, 22: 2362.; La Rosa, Corinna et al., The Journal of infectious diseases, 2012, 205: 1294-304). In addition, as a strong Th epitope derived from tetanus toxin, P2 is also commonly used in coupling with a target immunogen to enhance the immunogenicity (Panina-Bordignon P et al., Eur J Immunol, 1989, 19: 2237-42; La Rosa, Corinna et al., The Journal of infectious diseases, 2012, 205: 1294-304).

In general, however, a Th epitope used to increase the immunogenicity is usually heterologous. In other words, a high level of immune response against the Th epitope itself will not be produced in a vaccine subject. Thus, when a vaccine subject is vaccinated with a strong Th epitope as described above, it is likely that the immune system of vaccine subject is initially exposed to such a Th epitope, the activations against both such a Th epitope and a target immunogen in the recipient immune system are substantially synchronized, and the generation time and numbers of T cells against such a Th epitope are similar to those against the target immunogen. In this way, the effect on assisting the target immunogen will be limited, accordingly. Especially for a weakly immunogenic tumor antigen, the helping effect of such a Th epitope is more difficult to exert. Indeed, the direct use of a strong Th epitope, although being capable of activating a tumor antigen, elicits a lower level of cellular immune response that do not meet the needs of a tumor vaccine (Ghaffari-Nazari H et al., PLoS ONE, 2015, 10 (11): e0142563).

Thus, new Th epitope strategies are needed to enhance the immunogenicities of target immunogens, particularly some weak immunogens, such as tumor antigens.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a fusion peptide of CD4 helper T cell epitopes, by which the immunogenicity of a target immunogen is enhanced.

Further, the present invention utilizes a strong Th epitope derived from cytomegalovirus (CMV) and influenza (Flu) virus (influvirus) to obtain an epitope fusion peptide for enhancing the immunogenicity of a target immunogen.

For the purposes of the present invention, the following terms are defined below.

“Epitope fusion peptide” refers to a peptide formed by joining together several epitopes.

“Target immunogen” refers to an immunogen used for achieving a certain immune response, including a substance having an immunological activity, such as an antigen, preferably a protein.

It is another object of the present invention to provide a fusion protein of the epitope fusion peptide and the target immunogen.

To achieve the above object, the present invention provides a fusion peptide of CD4 helper T cell epitopes, comprising a CMV epitope and/or an influenza virus epitope.

In one embodiment of the present invention, the epitope fusion peptide comprises one or more of CMV epitopes selected from those shown in SEQ ID NOs: 1-10, and/or one or more of influenza virus epitopes selected from those shown in SEQ ID NOs: 11-23.

In one embodiment of the present invention, the epitope fusion peptide consists of one or more of CMV epitopes selected from those shown in SEQ ID NOs: 1-10, and/or one or more of influenza virus epitopes selected from those shown in SEQ ID NOs: 11-23. Preferably, the epitope fusion peptide consists of 5 or 10 CMV epitopes, and/or 8 or 13 influenza virus epitopes, such as the epitope fusion peptide shown in SEQ ID NO: 34 or 44. Most preferably, the epitope fusion peptide consists of 13 influenza virus epitopes, such as the epitope fusion peptide shown in SEQ ID NO: 48.

Preferably, the epitope fusion peptide induces a humoral or cellular immune response.

The present invention also provides a fusion protein of the epitope fusion peptide and a target immunogen.

The present invention also provides a polynucleotide encoding the epitope fusion peptide and/or the fusion protein.

In one embodiment of the present invention, the target immunogen is any one or more immunogens. Preferably, the target immunogen is a peptide, an antigen, a hapten, a carbohydrate, a protein, a nucleic acid, an allergen, a virus or a part of a virus, a bacterium, a parasite or other whole microorganism. In one embodiment of the present invention, the antigen is a tumor antigen or an infection-related antigen.

In one embodiment of the present invention, the tumor antigen is one or more tumor antigens selected from lung cancer antigen, testicular cancer antigen, melanoma antigen, liver cancer antigen, breast cancer antigen or prostate cancer antigen.

In one embodiment of the present invention, the tumor antigen is one or more tumor antigens selected from LAGE antigen, MAGE antigen or NY-ESO-1 antigen. Preferably, the LAGE antigen is LAGE-1, and the MAGE antigen is MAGE-A3. Further preferably, the tumor antigen comprises LAGE-MAGE-A3 and NY-ESO-1. Preferably, the amino acid sequence of LAGE-1 is shown in SEQ ID NO: 24, the amino acid sequence of MAGE-A3 is shown in SEQ ID NO: 25, and the amino acid sequence of NY-ESO-1 is shown in SEQ ID NO: 26.

In one embodiment of the present invention, the infection-related antigen is one or more infection-related antigen selected from an HIV antigen, a Flu virus antigen or an HBV antigen.

Preferably, the fusion protein is as shown in one of SEQ ID NOs: 55-58.

Another object of the present invention is to provide an immunogenic composition comprising a therapeutically effective amount of the epitope fusion peptide, the fusion protein and/or the polynucleotide according to the present invention, and a pharmaceutically acceptable carrier. Preferably, the immunogenic composition is a vaccine.

It is another object of the present invention to provide a kit comprising the epitope fusion peptide, the fusion protein, the polynucleotide and/or the immunogenic composition according to the present invention, and instructions for use thereof.

The present invention also provides use of the epitope fusion peptide, the fusion protein, the polynucleotide and/or the immunogenic composition according to the present invention in the manufacture of a medicament or a vaccine for increasing the immunogenicity of a target immunogen.

The present invention also provides a method for increasing the immunogenicity of a target immunogen using the epitope fusion peptide according to the present invention, comprising using a CD4 helper T cell epitope having a stronger immune response in a vaccine subject or population with a target immunogen to form a fusion protein. The method specifically comprises the following steps of:

(1) selecting one or more CD4 helper T cell epitopes, wherein a complex formed by combining the epitopes with MHC molecules can be recognized by CD4 helper T cell receptors, and a T cell immune response has been generated against at least one of the epitopes in a vaccine subject before vaccination;

(2) fusing the epitopes to prepare an epitope fusion peptide, fusing the epitope fusion peptide with a target immunogen to prepare a fusion protein, expressing the fusion protein and preparing it into a vaccine, wherein the expression vector can be in the form of a DNA vaccine vector, a protein vaccine vector or a virus vaccine vector; and

(3) vaccinating the vaccine subject with the above vaccine, and a suitable adjuvant, such as incomplete Freund's adjuvant, complete Freund's adjuvant, or aluminum hydroxide adjuvant and the like that can be selected for vaccination.

Further, step (1) in the method further comprises a step of examining the MHC phenotype of the vaccine subject. Preferably, examining the MHC phenotype of the vaccine subject comprises examining the MHC class II gene subtype of the vaccine subject.

The present invention also provides a method for treating or preventing a condition in a subject in need thereof, comprising administering a therapeutically effective amount of the epitope fusion peptide, the fusion protein, the immunogenic composition and/or the polynucleotide of the present invention. Preferably, the condition is one or more conditions selected from malignant tumors, and bacterial and viral chronic infections. Preferably, the malignant tumor is breast cancer or colon cancer. Preferably, in the method, the DNA vaccine vector is used for the prime immunization, and a protein vaccine vector is used for the boost immunization. More preferably, the pVKD1.0-C1-hMNB DNA vaccine is used for the prime immunization, and the LMNB-I13 protein is used for the boost immunization. The epitope fusion peptide provided by the present invention can substantially improve the level of cellular immune response to a target immunogen, particularly a weak immunogen, and is an effective means for overcoming the immune tolerance of immune system to an antigen, particularly to a tumor antigen or an infection-related antigen, and is suitable for efficiently enhancing the efficacy of a vaccine.

DESCRIPTION OF DRAWINGS

Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

FIGS. 1 and 2 are a plasmid map and a map of double enzyme digestion for identification of the DNA vaccine vector pVKD1.0-hLMN carrying the encoding sequences of LAGE-1, MAGE-A3 and NY-ESO-1 antigens, respectively.

FIGS. 3 and 4 are a plasmid map and a map of double enzyme digestion for identification of the DNA vaccine vector pVKD1.0-hLMN-CTB carrying the encoding sequences of LAGE-1, MAGE-A3 and NY-ESO-1 antigens and cholera toxin subunit B, respectively.

FIGS. 5 and 6 are a plasmid map and a map of double enzyme digestion for identification of the DNA vaccine vector pVKD1.0-C1 carrying the encoding sequences of CMV and Flu virus-derived CD4 epitopes, respectively.

FIGS. 7 and 8 are a plasmid map and a map of double enzyme digestion for identification of the DNA vaccine vector pVKD1.0-C1-LMNB carrying the encoding sequences of LAGE-1, MAGE-A3 and NY-ESO-1 antigens, cholera toxin subunit B, and CMV and Flu virus-derived CD4 epitopes, respectively.

FIGS. 9 and 10 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-LMN carrying the encoding sequences of LAGE-1, MAGE-A3 and NY-ESO-1 antigens, respectively.

FIGS. 11 and 12 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-LMN-CTB carrying the encoding sequences of LAGE-1, MAGE-A3 and NY-ESO-1 antigens and cholera toxin subunit B, respectively.

FIGS. 13 and 14 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-CMV Th carrying the encoding sequence of a CMV-derived epitope, respectively.

FIGS. 15 and 16 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-CMV10-LMNB carrying the encoding sequences of a CMV-derived epitope, LAGE-1, MAGE-A3 and NY-ESO-1 antigens, and cholera toxin subunit B, respectively.

FIGS. 17 and 18 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-CMV Th carrying the encoding sequences of a Flu virus-derived epitope, respectively.

FIGS. 19 and 20 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-Influ8-LMNB carrying the encoding sequences of a Flu virus-derived epitope, LAGE-1, MAGE-A3 and NY-ESO-1 antigens, and cholera toxin subunit B, respectively.

FIGS. 21 and 22 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-Influ13-LMNB carrying the encoding sequences of a Flu virus-derived epitope, LAGS-1, MAGE-A3 and NY-ESO-1 antigens, and cholera toxin subunit B, respectively.

FIG. 23 shows the detection results of cellular immune responses in the animal immunization experiment.

FIGS. 24 and 25 are a plasmid map and a map of double enzyme digestion for identification of the prokaryotic vector pET-30a(+)-CMV5-LMNB carrying the encoding sequences of a CMV-derived epitope, LAGE-1, MAGE-A3 and NY-ESO-1 antigens, and cholera toxin subunit B, respectively.

FIG. 26 shows the detection results of cellular immune responses in the animal immunization experiment in Example 12.

FIG. 27 shows the tumor growth of mice in Example 13.

FIGS. 28 and 29 show the tumor-free survival and overall survival of mice in Example 13, respectively.

FIG. 30 shows the tumor growth of mice in each treatment group for the 4T1-hNY-ESO-1 mouse tumor model.

FIG. 31 shows the tumor growth of mice in each treatment group for the CT26-hLAGE-1 mouse tumor model.

SPECIFIC EMBODIMENTS

The present invention is described in further detail below with reference to the specific embodiments. The examples are given for the purpose of illustration of the present invention only, and are not intended to limit the scope of the present invention.

Example 1 Construction of DNA Vaccine pVKD1.0-hLMN

The amino acid sequences of LAGE-1, MAGE-A3 and NY-ESO-1 are shown in SEQ ID NOs: 24-26, respectively. By means of an online codon optimization software referred to as the Java Codon Adaption Tool, the nucleotide sequences for mammalian codon usage preference as shown in SEQ ID NOs: 27-29 respectively were obtained by optimization based on the above antigen amino acid sequences. The nucleotide sequences were synthesized by Shanghai Generay Biotech Co., Ltd., and then cloned between the multiple cloning sites Sal I and BamH I on the DNA vaccine vector pVKD1.0 (provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park) by a method well known in the art to construct the DNA vaccine vector pVKD1.0-hLMN capable of expressing the fusion protein as an antigen (the plasmid map is shown in FIG. 1), which was stored after being sequenced for identification. The vector pVKD1.0-hLMN was identified by the restriction endonucleases Sal I and BamH I (the enzyme digestion system is shown in Table 1), and its enzyme digestion map for verification is shown in FIG. 2.

TABLE 1 Enzyme digestion system for identification of the plasmid pVKD1.0-hLMN (enzyme digestion at 37° C., 2 h) Enzyme digestion system Volume Plasmid pVKD1.0-hLMN 3 μL, about 1 μg Sal I (Takara, Cat. No. 1080A) 1 μL BamH I (Takara, Cat. No. 1010A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 2 Construction of DNA Vaccine pVKD1.0-hLMN-CTB

The mammalian codon optimized sequence (SEQ ID NO: 31) of the amino acid sequence (SEQ ID NO: 30) of cholera toxin subunit B (CTB) and its eukaryotic expression vector pVKD1.0-CTB were provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park. The primers were designed by using pVKD1.0-CTB as a template (see Table 2). The CTB gene fragment was amplified by PCR, and the corresponding fragment was then recovered from the gel. The CTB fragment was inserted into a corresponding position on the linearized vector pVKD1.0-hLMN by a homologous recombination method, to construct the DNA vaccine vector pVKD1.0-hLMN-CTB (the plasmid map is shown in FIG. 3), which was stored after being sequenced for identification. The vector pVKD1.0-hLMN-CTB was identified by the restriction endonucleases Sal I and BamH I (the enzyme digestion system is shown in Table 3), and its enzyme digestion map for verification is shown in FIG. 4.

TABLE 2 Primers in Example 2 Primer Sequence 1F (SEQ ID TCCCTCAGGGCAGAGGCGCATCAAGCTGAAGTTCGG NO: 32) CGTG IR (SEQ ID GAAGGCACAGCAGATCTGGATCCTCAGTTGGCCATG NO: 33) CTGATGGC

TABLE 3 Enzyme digestion system for identification of plasmid pVKD1.0-hLMN-CTB (enzyme digestion at 37° C., 2 h) Enzyme digestion system Volume Plasmid pVKD1.0-hLMN-CTB 3 μL, about 1 μg Sal I (Takara, Cat. No. 1080A) 1 μL BamH I (Takara, Cat. No. 1010A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 3 Construction of DNA Vaccine pVKD1.0-CI-LMNB

The strong Th epitopes derived from cytomegalovirus (CMV) and influenza (Flu) virus (see Table 4) were obtained from an immune epitope database (IEDB), wherein the strong Th epitopes of CMV include pp65-11, pp65-71, pp65-92, pp65-123, pp65-128, pp65-57, pp65-62, pp65-30, pp65-112 and pp65-104, and the strong Th epitopes of Flu virus include HA203, NP438, NS1-84, M1-181, HA375, NP24, NP95, NP221, HA434, HA440, NP324, M1-127 and M1-210. The selected epitopes in Table 4 cover most subtypes of MHC class II molecules in both human and mouse. The selected epitopes pp65-11, pp65-′71, pp65-92, pp65-123, pp65-128, HA203, NP438, NS1-84, M1-181, HA375, NP24, NP95, NP221 were then linked together in tandem to form an fusion peptide of CMV virus epitopes and Flu virus epitopes having the amino acid sequence shown in SEQ ID NO: 34. The epitope fusion peptide was subjected to mammal codon optimization to give the nucleic acid sequence shown in SEQ ID NO: 35, which was sent to Suzhou Synbio Technologies Co., Ltd for synthesis, and then inserted into the DNA vaccine vector pVKD1.0 (Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park) by a molecular biology method well known in the art to form the vector pVKD1.0-CI (the plasmid map is shown in FIG. 5), and stored after being sequenced for identification. The vector pVKD1.0-CI was identified by the restriction endonucleases Pst I and Bgl II (the enzyme digestion system is shown in Table 5) and its enzyme digestion map for verification is shown in FIG. 6.

TABLE 4 Th Epitopes in Example 3 Epitope Name Source Amino acid sequence pp65-11 CMV LLQTGIHVRVSQPSL (SEQ ID NO: 1) pp65-71 CMV IIKPGKISHIMLDVA (SEQ ID NO: 2) pp65-92 CMV EHPTFTSQYRIQGKL (SEQ ID NO: 3) pp65-123 CMV AGILARNLNPMVATV (SEQ ID NO: 4 pp65-128 CMV KYQEFFWDANDIYRI (SEQ ID NO: 5) pp65-57 CMV KVYLESFCEDVPSGK (SEQ ID NO: 6) pp65-62 CMV TLGSDVEEDLTMTRN (SEQ ID NO: 7) pp65-30 CMV PLKMLNIPSINVHHY (SEQ ID NO: 8) pp65-112 CMV ACTSGVMTRGRLKAE (SEQ ID NO: 9) pp65-104 CMV TERKTPRVTGGGAMA (SEQ ID NO: 10) HA203 Influ NQRALYHTENAYVSVVS (SEQ ID NO: 11) NP438 Influ SDMRAEIIKMMESARPE (SEQ ID NO: 12) NS1-84 Influ ALASRYLTDMTIEEMSR (SEQ ID NO: 13) M1-181 Influ LASTTAKAMEQMAGSSE (SEQ ID NO: 14) HA375 Influ SGYAADQKSTQNAINGITNKVN (SEQ ID NO: 15) NP24 influ EIRASVGKMIDGIGRFYI (SEQ ID NO: 16) NP95 influ PIYRRVDGKWMRELVLY (SEQ ID NO: 17) NP221 Influ RMCNILKGKFQTAAQRAM (SEQ ID NO: 18) HA434 Influ IWTYNAELLVLLENERT (SEQ ID NO: 19) HA440 Influ ELLVLLENERTLDFHDS (SEQ ID NO: 20) NP324 Influ HKSQLVWMACNSAAFED (SEQ ID NO: 21) M1-127 Influ CMGLIYNRMGAVTTESA SEQ ID NO: 22) M1-210 Influ RQMVQAMRAIGTHPSSSTGLKND SEQ ID NO: 23)

TABLE 5 Enzyme digestion system for identification of plasmid pVKD1.0-CI (enzyme digestion at 37° C., 2 h) Enzyme digestion system Volume Plasmid pVKD1.0-CI 3 μL, about 1 μg Pst I (Takara, Cat. No. 1073A) 1 μL Bgl II (Takara, Cat. No. 1021A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Finally, the primers were designed by using the vector pVKD1.0-hLMN-CTB in Example 2 as a template (see table 6). The target gene fragment hLMN-CTB was amplified by PCR, and was then inserted between the restriction sites Not I and Bam HI on the pVKD1.0-CI vector by a molecular biology method well known in the art to construct the DNA vaccine vector pVKD1.0-CI-LNINB (the plasmid map is shown in FIG. 7), which was stored after being sequenced for identification. The vector pVKD1.0-CI-LMNB was identified by the restriction endonucleases Bam HI and EcoR V (the enzyme digestion system is shown in Table 7), and its enzyme digestion map for verification is shown in FIG. 8.

TABLE 6 Primers in Example 3 Primer Sequence 3F (SEQ ID GCGCGGCCGCTGTCACCGTCGTCGACATGCAGGCCG NO: 36) AA 3R (SEQ ID GCGATCCTCAGTTGGCCATGCTGATGGCGGCGATG NO: 3

TABLE 7 Enzyme digestion system for identification of plasmid pVKD1.0-CI-LMNB (enzyme digestion at 37° C., 2 h) Enzyme digestion system Volume Plasmid pVKD1.0-CI-LMNB 3 μL, about 1 μg Bam HI (Takara, Cat, No. 1010A) 1 μL EcoR V (Takara, Cat. No. 1042A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 4 Construction of LMN Prokaryotic Expression Vector

The amino acid sequences of LAGE-1, MAGE-A3 and NY-ESO-1 are shown in SEQ ID NOs: 24-26, respectively. By means of an online codon optimization software referred to as the Java Codon Adaption Tool, the nucleotide sequences for E. coli codon usage preference shown in SEQ ID NOs: 38-40 respectively were obtained through optimization based on the antigen amino acid sequences. The nucleotide sequences were synthesized by Suzhou Synbio Technologies Co., Ltd., and then inserted between the multiple cloning sites Nco I and Xho I on the prokaryotic expression vector pET-30a(+) (Novagen, Cat. No. 69909) by a molecular biology method well known in the art to construct the prokaryotic expression construct pET-30a(+)-LMN (the plasmid map is shown in FIG. 9), which was stored after being sequenced for identification. The vector pET-30a(+)-LMN was identified by the restriction endonucleases Nco I and Xho I (the enzyme digestion system is shown in Table 8), and its enzyme digestion map for verification is shown in FIG. 10.

TABLE 8 Enzyme digestion system for identification of plasmid pET-30a(+)-LMN (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-LMN 3 μL, about 1 μg Nco I (Takara, Cat. No. 1160A) 1 μL Xho I (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 5 Construction of LMN-CTB Prokaryotic Expression Vector

The amino acid sequence of cholera toxin subunit B (CTB) (SEQ ID NO: 30) and its prokaryotic codon optimized nucleic acid sequence (SEQ ID NO: 41) were provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park. The primers were designed (see table 9), and a nucleic acid fragment containing the CTB encoding sequence was amplified by a PCR method using the pET-30a(+)-CTB (Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park) as a template, and the instructions of Ex Taq Enzyme Reagent (Takara, Cat. No. RR001B) were referred to for the specific method. The nucleic acid fragment was then inserted into the pET-30a(+)-LMN vector by means of homologous recombination to construct the pET-30a(+)-LMN-CTB vector (the plasmid map is shown in FIG. 11), which was stored after being sequenced for identification. The vector pET-30a(+)-LMN-CTB was identified by the restriction endonucleases Nco I and Xho I (the enzyme digestion system is shown in Table 10), and its enzyme digestion map for verification is shown in FIG. 12.

TABLE 9 Primers in Example 5 Primer Sequence 5F (SEQ ID GGTGGTGGTGGTGCTCGAGTTAGTTAGCCATAGAGA NO: 42) 5R (SEQ ID TCTGCGTGAAGGTGAAGAAGCTCAGGCTGAAGGTCG NO: 43) TGG

TABLE 10 Enzyme digestion system for identification Example 5 (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-LMN-CTB 3 μL, about 1 μg Nco I (Takara, Cat. No. 1160A) 1 μL Xho 1 (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 6 Construction of Prokaryotic Expression Vector Containing Fusion Protein of LMN-CTB and CMV Th Epitopes

Ten (10) CMV-derived Th epitopes pp65-11, pp65-71, pp65-92, pp65-123, pp65-128, pp65-57, pp65-62, pp65-30, pp65-112 and pp65-104 were selected from Table 4, and linked together in tandem to form the amino acid sequence shown in SEQ ID NO: 44, wherein the sequence segment “EFELRRQ” in SEQ ID NO: 44 is formed due to the introduction of enzyme restriction site, which belongs to a common technique for fusion and construction. By means of an online codon optimization software referred to as the Java Codon Adaption Tool, the nucleotide sequence for E. coli codon usage preference (SEQ ID NO: 45) was obtained through optimization based on the amino acid sequence of Th epitopes. The nucleotide sequence was synthesized by Shanghai Generay Biotech Co., Ltd., and then inserted between the multiple cloning sites Nco I and Xho I on the prokaryotic expression vector pET-30a(+) (Novagen, Cat. No. 69909) by a molecular biology method well known in the art to construct the prokaryotic expression construct pET-30a(+)-CMV Th (the plasmid map is shown in FIG. 13) capable of expressing the fusion protein as an antigen, which was stored after being sequenced for identification. The vector pET-30a (+)-CMV Th was identified by the restriction endonucleases Mlu I and Xho I (the enzyme digestion system is shown in Table 11), and its enzyme digestion map for verification is shown in FIG. 14.

As shown in FIG. 13, CMV Th1 contains 5 CMV Th epitopes consisting of pp65-1L pp65-71, pp65-92, pp65-123 and pp65-128 in tandem, and CMV Th2 contains 5 CMV Th epitopes consisting of pp65-57, pp65-62, pp65-30, pp65-112 and pp65-104. Three restriction enzyme sites such as EcoR I, Sac I and Sal I were introduced between CMV Th1 and CMV Th2.

TABLE 11 Enzyme digestion system for identification of plasmid pET-30a(+)-CMV Th (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-CMV Th 3 μL, about 1 μg Mlu I (Takara, Cat. No. 1071A) 1 μL Xho I (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

The Primers were designed (see Table 12), and a nucleic acid fragment containing the LMN-CTB encoding sequence was amplified by a PCR method using pET-30a(+)-LMN-CTB in Example 5 as a template, and the instructions of Ex Taq Enzyme Reagent (Takara, Cat. No. RR001B) were referred to for the specific method. The nucleic acid fragment was then inserted between Not I and Xho I on the pET-30a(+)-CMV Th vector in Example 6 by a molecular biology method well known in the art to construct the pET-30a(+)-CMV10-LMNB vector (the plasmid map is shown in FIG. 15), which was stored after being sequenced for identification. The vector pET-30a(+)-CMV10-LMNB was identified by the restriction endonucleases BamH I and Xho I (the enzyme digestion system is shown in Table 13) and its enzyme digestion map for verification is shown in FIG. 16. As shown in FIG. 15, pET-30a(+)-CMV10-LMNB contains CMV Th1 and CMV Th2 fragments, i.e. all 10 CMV Th epitopes in Table 4. These epitopes are pp65-11, pp65-71, pp65-92, pp65-123, pp65-128, pp65-57, pp65-62, pp65-30, pp65-112 and pp65-104.

TABLE 12 Primer design in Example 6 Primer Sequence 6F (SEQ ID NO: 46 GCGCGGCCGCGACGACAAGGCCATGGCT 6R (SEQ ID NO: 47) GCCTCGAGGTTAGCCATAGAGATAGC

TABLE 13 Enzyme digestion system for identification of pET-30a(+)-CMV10-LMNB (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-CMV10-LMNB 3 μL, about 1 μg BamH I (Takara, Cat. No. 1010A) 1 μL Xho I (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 7 Construction of Prokaryotic Expression Vector Containing Fusion Protein of LMN-CTR and Influ Th Epitopes

Thirteen (13) Th Epitopes derived from Flu virus, HA203, NP438, NS1-84, M1-181, HA375, NP24, NP95, NP221, HA434, HA440, NP324, M1-127 and M1-210 were selected from Table 4, and linked together in tandem to form the amino acid sequence shown in SEQ ID NO: 48. By means of an online codon optimization software referred to as the Java Codon Adaption Tool, the nucleotide sequence for E. coli codon usage preference (SEQ ID NO: 49) was obtained through optimization based on the amino acid sequence containing Flu virus Th epitopes. The nucleotide sequence was synthesized by Shanghai Generay Biotech Co., Ltd., and then inserted between the multiple cloning sites Nco I and Xho I on the prokaryotic expression vector pET-30a(+) (Novagen, Cat. No. 69909) by a molecular biology method well known in the art to construct the prokaryotic expression construct pET-30a(+)-Influ Th (the plasmid map is shown in FIG. 17) capable of expressing the fusion protein as an antigen, which was stored after being sequenced for identification. The vector pET-30a(+)-Influ Th was identified by the restriction endonucleases Nco I and Xho I (the enzyme digestion system is shown in Table 14), and its enzyme digestion map for verification is shown in FIG. 18.

As shown in FIG. 17, Influ Th1 contains 8 Flu virus Th epitopes consisting of HA203, NP438, HA375, NP24, NP95 and NP221 in tandem, and Influ Th2 contains 5 Flu virus Th epitopes consisting of RA434, HA440, NP324, M1-127 and M1-210. Three restriction sites such as EcoR 1, Sac I and Sal I were introduced between Influ Th1 and Influ Th2.

TABLE 14 Enzyme digestion system for identification in Example 7 (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-Influ Th 3 μL, about 1 μg Nco I (Takara, Cat. No. 1160A) 1 μL Xho I (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

The primers were designed (see Table 15), and a nucleic acid fragment containing the LMN-CTB encoding sequence was amplified by a PCR method using pET-30a(+)-LMN-CTB in Example 5 as a template, and the instructions of Ex Taq Enzyme Reagent (Takara, Cat. No. RR001B) were referred to for the specific method. The nucleic acid fragment was then inserted between Not I and Sal I on the pET-30a(+)-Influ Th vector in Example 7 by a molecular biology method well known in the art to construct the pET-30a(+)-Influ8-LMNB vector (containing 8 Flu virus Th epitopes; the plasmid map is shown in FIG. 19), which was stored after being sequenced for identification. The vector pET-30a(+)-Influ8-LMNB was identified by the restriction endonucleases BamH I and Xho I (the enzyme digestion system is shown in Table 16) and its enzyme digestion map for verification is shown in FIG. 20. As shown in FIG. 19, the pET-30a(+)-Influ8-LMNB vector contains the Influ Th1 segment, i.e., 8 Flu virus Th epitopes including HA203, NP438, NS1-84, M1-181, HA375, NP24, NP95, and NP221 in Table 4.

TABLE 15 Primers in Example 7 Primer Sequence 7F1 (SEQ ID NO; 50) GGCGGCCGCGTTAGCCATAGAGATAGC 7R1 (SEQ ID NO: 51) GCGTCGACAAGACGACAAGGCCATGGC TATGC

TABLE 16 Enzyme digestion system for identification of plasmid pET-30a(+)-Influ8-LMNB (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-Influ8-LMNB 3 μL, about 1 μg BamH I (Takara, Cat. No. 1010A) 1 μL Xho I (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

The primers were designed (see Table 17), and a nucleic acid fragment containing the LMN-CTB encoding sequence was amplified by a PCR method using pET-30a(+)-LMN-CTB in Example 5 as a template, and the instructions of Ex Taq Enzyme Reagent (Takara, Cat. No. RR001B) was referred to for the specific method. This nucleic acid fragment was then inserted between Not I and Xho I on the pET-30a(+)-Influ Th vector in Example 6 by a molecular biology method well known in the art to construct the pET-30a(+)-Influ13-LMNB vector (containing 13 Flu virus Th epitopes; the plasmid map is shown in FIG. 21), which was stored after being sequenced for identification. The vector pET-30a(+)-CMV10-LMNB was identified by the restriction endonucleases BamH I and Xho I (the enzyme digestion system is shown in Table 18) and its enzyme digestion map for verification is shown in FIG. 22.

As shown in FIG. 21, the pET-30a(+)-Influ13-LMNB vector contains both the Influ Th1 and Influ Th2 segments, i.e., 8 Flu virus Th epitopes including HA203, NP438, NS1-84, M1-181, HA375, NP24, NP95, and NP221 in Table 4, and 5 Flu virus Th epitopes including HA434, HA440, NP324, M1-127 and M1-210 in Table 4, The vector includes all 13 Flu virus Th epitopes in total in Table 4

TABLE 17 Primer design in Example 7 Primer Sequence 7F2 (SEQ ID NO: 52) GCCTCGAGGTTAGCCATAGAGATAGCA 7R2 (SEQ ID NO: 53) GCGCGGCCGCGACGACAAGGCCATGGC TATG

TABLE 18 Enzyme digestion system for identification in Example 7 (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-Influ13-LMNB 3 μL, about 1 μg BamH I (Takara, Cat. No. 1010A) 1 μL Xho I (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 8 Expression and Purification of Fusion Protein

The prokaryotic expression vector pET-30a(+)-LMN constructed in Example 4, the prokaryotic expression vector pET-30a(+)-LMN-CTB constructed in Example 5, the prokaryotic expression vectors pET-30a(+)-CMV5-LMNB and pET-30a(+)-CMV10-LMNB constructed in Example 6, the prokaryotic expression vectors pET-30a(+)-Influ8-LMNB and pET-30a(+)-Influ13-LMNB constructed in Example 7 were respectively transformed into BL21 (DE3) competent cells (Tiangen Biotech (Beijing) Co., Ltd., Cat. No. CB105; the instructions of competent cells were referred to for the transformation method) to prepare the recombinant proteins LMN (its amino acid sequence is shown in SEQ ID NO: 59), LMNB (its amino acid sequence is shown in SEQ ID NO: 54), LMNB-C10 (its amino acid sequence is shown in SEQ ID NO: 58), LMNB-18 (its amino acid sequence is shown in SEQ ID NO: 55), and LMNB-13 (its amino acid sequence is shown in SEQ ID NO: 56) according to the pET System Manual (TB055 8th Edition February 1999, Novagen respectively, which were stored at −80° C. after subpackage.

The concentrations of the recombinant proteins prepared are 1 mg/mL, as detected by a BCA method (Beyotime Institute of Biotechnology, Cat. No. P0009), and the instructions of detection kit were referred to for the detection method. The contents of endotoxin in the prepared recombinant proteins were less than IEU/mg, as measured by a gel method (Chinese Horseshoe Crab Reagent Manufactory Co., Ltd., Xiamen, Cat. No. G011000), which meet the requirements of an animal experiment, and the instructions of horseshoe crab agent were referred to for the detection method.

Example 9 Animal Immunization Experiment

The information of the vaccines prepared in Examples 2, 3 and 8 is shown in Table 19. The DNA vaccine vector pVKD1.0 was provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park, and the Flu antigen NP (NCBI reference sequence: YP_009118476.1) of the DNA vaccine pVKD1.0-NP (the expression is derived from the virus strain A/Shanghai/02/2013 (H7N9)) was provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park, and the protein vaccine VP1 (VP1 protein of enterovirus 71, see the Chinese Patent Application No. 201310088364.5) was provided by the Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park.

Sixteen (16) 6-8 weeks old female BAL B/c mice were purchased from the Laboratory Animal Center of Suzhou University and raised in the SPF animal house of the Laboratory Animal Center of Suzhou University. The experimental animal grouping and vaccination schemes are shown in Table 20. All DNA vaccines were injected into the tibialis anterior muscle of the calf at 100 μg/animal. All protein vaccines were fully emulsified with complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA) and injected subcutaneously into the back at 10 μg/animal. Two weeks after the last immunization, the mice were sacrificed, and their serum and splenocytes were collected for an enzyme-linked immunospot (ELISPOT) assay and an enzyme-linked immunosorbent assay (ELISA), respectively. The mouse IFN-γ ELISPOT kit was purchased from BD, USA (Cat. No. 551083), and the instructions of IFN-γ ELISPOT kit from BD were referred to for the method. The stimulating peptide was NY-ESO-1 41# peptide (WITQCFLPVFLAQPP) synthesized by Shanghai Science Peptide Biological Technology Co., Ltd., with the final concentration of 10 μg/mL. The positive stimuli phorbol-12-myristate-13-acetate (PMA) and ionomycin were purchased from Sigma, USA.

An ELISA method is well known for a person skilled in the art, and is briefly described below. The 96-Well ELISA plates were purchased from Jianghai Glass Instrument General Factory. Both the recombinant LMN and NY-ESO-1 were provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park. The plates were coated with the proteins in NaHCO₃ buffer (pH 9.6) at 4° C. overnight at a coating concentration of 10 μg/mL, followed by blocking with 0.1% bovine serum albumin (BSA) in phosphate buffered saline (PBS) at 37° C. for 30 minutes and then washing 5 times with 0.5% Tween 20 in phosphate buffered saline (PBST). An incubation with the mouse serum at room temperature was carried out for 1 hour at an initial dilution of 1:100 and washed 5 times with PBST, and another incubation with goat anti-mouse HRP secondary antibody (Santacruz, USA) was carried out at 1:5000 at 37° C. for 30 min. After being washing 5 times with PBST, the substrate was developed with 3,3,5,5-tetramethylbenzidine (TMB) at 37° C. for 15 min and stopped with 2M dilute sulfuric acid, and then the absorbance (A) values were read at 450 nm using a microplate reader (Thermo, USA). A value which is 2.1 times greater than the negative control A value was judged to be positive, and the reciprocal of the highest dilution with respect to the positive values was defined as the serum antibody titer. A titer was defined as 50 when it was less than the initial dilution of 1:100.

TABLE 19 Vaccine information Vaccine Attribute Antigen CD4 Th epitope pVKD1.0-LMN-CTB DNA LAGE-1, Epitope-free MAGE-A3, NY-ESO-1, pVKD1.0-CI-LMNB DNA LAGE-1, 5 CMV epitopes, MAGE-A3, 8 influenza virus NY-ESO-1 epitopes pVKD1.0-CI DNA None 5 CMV epitopes, 8 influenza virus epitopes pVKD1.0-NP DNA NP 5 influenza virus epitopes LMNB Recombinant LACE-1, Epitope-free protein MAGE-A3, NY-ESO-1 LMNB-18 Recombinant LAGE-1, First 8 influenza protein MAGE-A3, virus epitopes NY-ESO-1 LMNB-I13 Recombinant LAGE-1, 13 influenza virus protein MAGE-A3, epitopes NY-ESO-1 LMNB-C5 Recombinant LAGE-1, First 5 CMV protein MAGE-A3, epitopes NY-ESO-1 LMNB-C10 Recombinant LAGE-1, 10 CMV epitopes protein MAGE-A3, NY-ESO-1 VP1 Recombinant VP1 Epitope-free protein

TABLE 20 Grouping and immunization schemes Week 0, 4, 8 Week 12, 16, 20 Week 24 Week 28 Grouping Vaccine Dose Vaccine Dose Vaccine Dose Vaccine Dose A(n = 4) pVKD1.0-NP 100 μg pVKD1.0 100 μg VP1/CFA 100 μg VPI/IFA 100 μg B(n = 4) pVKD1.0-NP 100 μg pVKD 1.0- 100 μg LMNB/CFA 100 μg LMNB/IFA 100 μg LMNB C(n = 4) pVKD1.0-NP 100 μg pVKD 1.0- 100 μg LMNB- 100 μg LMNB- 100 μg CI-LMNB I8/CFA I8/IFA D(n = 4) pVKD1.0-NP 100 μg pVKD 1.0- 100 μg LMNB- 100 μg LMNB- 100 μg CI-LMNB I13/CFA I13/IFA

The results of cellular immune response assay are shown in FIG. 23. Among them, the group primed with pVKD1.0-CI-LMNB DNA vaccine and boosted with LMNB-I13 protein (i.e., group D in Example 8) had the best immune effect, which was significantly higher than those of the parallel control group (group B) and the group boosted with LMNB-18 (group C). Moreover, the level of cellular immune response in the group boosted with LMNB-I13 protein was nearly 3-fold higher than that in the parallel control group (group B). The results showed that a load of 13 Flu virus Th epitopes (group D) could significantly increase the cellular immune response level of weak immunogens.

Example 10 Construction of Prokaryotic Expression Vector Containing Fusion Protein of LMN-CTB and CMV Th Epitope

The primers were designed (see Table 21), and a nucleic acid fragment containing the LMN-CTB encoding sequence was amplified by a PCR method using pET-30a(+)-LMN-CTB in Example 5 as a template, and the instructions of Ex Taq Enzyme Reagent (Takara, Cat. No. RR001B) were referred to for the specific method. The nucleic acid fragment was then inserted between Not I and Sal I on the pET-30a(+)-CMV Th vector in Example 6 by a molecular biology method well known in the art to construct the pET-30a(+)-CMV5-LMNB vector (the plasmid map is shown in FIG. 24), which was stored after being sequenced for identification. The vector pET-30a(+)-CMV5-LMNB was identified by the restriction endonucleases BamH I and Xho I (the enzyme digestion system is shown in Table 22) and its enzyme digestion map for verification is shown in FIG. 25. As shown in FIG. 24, pET-30a(+)-CMV5-LMNB contains a CMV Th1 fragment, i.e. the first 5 CMV Th epitopes in Table 4. These epitopes are pp65-11, pp65-71, pp65-92, pp65-123 and pp65-128.

TABLE 21 Primer design in Example 10 Primer Sequence 7F1 (SEQ ID NO: 50) GCGCGGCCGCGTTAGCCATAGAGATAGC 7R1 (SEQ ID NO: 51) GCGTCGACAAGACGACAAGGCCATGGCT ATGC

TABLE 22 Enzyme digestion system for identification of pET-30a(+)-CMV10-LMNB (enzyme digestion at 37° C., overnight) Enzyme digestion system Volume Plasmid pET-30a(+)-CMV10-LMNB 3 μL, about 1 μg BamH I (Takara, Cat. No. 1010A) 1 μL Xho I (Takara, Cat. No. 1094A) 1 μL Enzyme digestion buffer 1 μL ddH₂O q.s. to 10 μL

Example 11 Expression and Purification of Fusion Protein

As described in Example 8, the prokaryotic expression vector pET-30a(+)-CMV5-LMNB constructed in Example 10 was transformed into BL21 (DE3) competent cells ('Tangen Biotech (Beijing) Co., Ltd., Cat. No. CB105; the instructions of competent cells were referred to for the transformation method) to prepare the recombinant protein LMNB-05 (its amino acid sequence is shown in SEQ ID NO: 57) according to the pET System Manual (TB055 8th Edition February 1999, Novagen), which was stored at −80° C. after subpackage.

The concentration of the recombinant protein prepared was 1 mg/mL, as detected by a BCA method (Beyotime Institute of Biotechnology, Cat. No. P0009), and the instructions of detection kit were referred to for the detection method. The content of endotoxin in the prepared recombinant protein was less than IEU/mg, as measured by a gel method (Chinese Horseshoe Crab Reagent Manufactory Co., Ltd., Xiamen, Cat. No. G011000), which met the requirements of an animal experiment, and the instructions of Horseshoe Crab agent were referred to for the detection method.

Example 12 Animal Immunization Experiment

The vaccine information is shown in Table 19. The DNA vaccine pVKD1.0-CI (Example 3) was provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park.

Twenty (20) 6-8 weeks old female BAL B/c mice were purchased from the Laboratory Animal Center of Suzhou University and raised in the SPF animal house of the Laboratory Animal Center of Suzhou University. The experimental animal grouping and vaccination schemes are shown in Table 23. All DNA vaccines were injected into the tibial anterior muscle of the calf at 1.00 μg/animal. All protein vaccines were fully emulsified with complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA), and injected subcutaneously into the back at 10 μg/animal. Two weeks after the last immunization, the mice were sacrificed, and serum and splenocytes were collected for an enzyme-linked immunospot (ELISPOT) assay and an enzyme-linked immunosorbent assay (ELISA), respectively. The mouse IFN-γ ELISPOT kit was purchased from BD, USA (Cat. No. 551083), and the instructions of IFN-γ ELISPOT kit from BD were referred to for the method. The stimulating peptide was NY-ESO-1 41# peptide (WITQCFLPVFLAQPP) synthesized by Shanghai Science Peptide Biological Technology Co., Ltd., with a final stimulating concentration of 10 μg/mL. The positive stimuli phorbol-12-myristate-13-acetate (PMA) and ionomycin were purchased from Sigma, USA.

An ELISA method is well known in the art and briefly described below. 96-Well ELISA plates were purchased from Jianghai Glass Instrument General Factory. Both recombinant LMN and NY-ESO-1 were provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park. The plates were coated with the proteins in NaHCO₃ buffer (pH 9.6) at 4° C. overnight at a coating concentration of 10 μg/mL, followed by blocking with 0.1% bovine serum albumin (BSA) in phosphate buffered saline (PBS) at 37° C. for 30 minutes and then washing 5 times with 0.5% Tween 20 in phosphate buffered saline (PBST). An incubation with mouse serum was carried out at room temperature for 1 hour at an initial dilution of 1:100 and washed 5 times with PBST. Another incubation with goat anti-mouse HRP secondary antibody (Santacruz, USA) was carried out at 1:5000 at 37° C. for 30 min, and washed 5 times with PBST. The substrate was then developed with 3,3,5,5-tetramethylbenzidine (TMB) at 37° C. for 15 min and stopped with 2M dilute sulfuric acid, and the absorbance (A) values were read at 450 nm using a microplate reader (Thermo, USA). A value which is 2 times greater than the negative control A value was judged to be positive, and the reciprocal of the highest dilution with respect to the positive values was defined as the serum antibody titer. A titer was defined as 50 when it was less than the initial dilution of 1:100.

TABLE 23 Grouping and immunization schemes Week 0, 4, 8 Week 12, 16, 20 Week 24 Week 28 Grouping Vaccine Dose Vaccine Dose Vaccine Dose Vaccine Dose A (n = 5) pVKD1.0-CI 100 μg pVKD1.0 100 μg VP1/CFA 100 μg VPI/IFA 100 μg B (n = 5) pVKD1.0-CI 100 μg pVKD1.0-LMNB 100 μg LMNB/CFA 100 μg LMNB/IFA 100 μg C (n = 5) pVKD1.0-CI 100 μg pVKD1.0-CI-LMNB 100 μg LMNB-C5/CFA 100 μg LMNB-C5/CFA 100 μg D (n = 5) PVKD1.0-CI 100 μg pVKD1.0-CI-LMNB 100 μg LMNB-C10/CFA 100 μg LMNB-C10/CFA 100 μg

The results of cellular immune response assay are shown in FIG. 26. Among them, the group primed with the pVKD1.0-CI-LMNB DNA vaccine, boosted with the LMNB-C5 protein (i.e. group C in Example 11) and boosted with the LMNB-C10 protein (i.e. group D in Example 11) had the best immune effect, which was significantly higher than that in the parallel control (group B). The results showed that a load of 5 CMV virus Th epitopes (group C) and 10 CMV virus Th epitopes (group D) could significantly improve the cellular immune response of weak immunogens.

Example 13 Animal Experiment for Tumor Prevention

The information of vaccines prepared in Examples 2, 3 and 8 is shown in Table 19. The DNA vaccine vector pVKD1.0 was provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park, and the Flu antigen NP (NCBI reference sequence: YP_009118476.1) of the DNA vaccine pVKD1.0-NP (the expression is derived from the virus strain A/Shanghai/02/2013 (H7N9)) was provided by Vacdiagn. Biotechnology Co., Ltd., Suzhou Industrial Park, and the protein vaccine VP1 (VP1 protein of enterovirus 71, see the Chinese Patent Application No. 201310088364.5) was provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park.

Sixty (60) 6-8 weeks old female BAL B/c mice were purchased from the Laboratory Animal Center of Suzhou University and raised in the SPF animal house of the Laboratory Animal Center of Suzhou University. The experimental animal grouping and vaccination schemes are shown in Table 24. All DNA vaccines were injected into the tibials anterior muscle of the calf at 100 μg/animal protein vaccines were fully emulsified with complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA) and injected subcutaneously into the back at 10 μg/animal. Two weeks after the last immunization, the mice were inoculated subcutaneously with the cell line transfected stably by 4T1-hNY-ESO-1 (provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park), at an inoculation dose of 1×10⁵ cells/mouse, and the tumor growth was continuously observed and measured after the inoculation. The tumor volume was calculated according to the following equation: tumor volume (mm³)=length×width²/2. The mice were sacrificed when the tumor volume exceeded 2000 mm³.

TABLE 24 Grouping and immunization schemes Week 0, 4, 8 Week 12, 16, 20 Week 24 Week 28 Grouping Vaccine Dose Vaccine Dose Vaccine Dose Vaccine Dose A (n = 10) pVKD1.0-NP 50 μg pVKD1.0 100 μg VP1/CFA 10 μg VP1/IFA 10 μg pVKD1.0-CI 50 μg B (n = 10) pVKD1.0-NP 50 μg pVKD1.0-LMNB 100 μg LMNB/CFA 10 μg LMNB/IFA 10 μg pVKD1.0-CI 50 μg C (n = 10) pVKD1.0-NP 50 μg pVKD1.0-CI-LMNB 100 μg LMNB-I8/CFA 10 μg LMNB-I8/IFA 10 μg pVKD1.0-CI 50 μg D (n = 10) pVKD1.0-NP 50 μg pVKD1.0-CI-LMNB 100 μg LMNB-I13/CFA 10 μg LMNB-I13/IFA 10 μg pVKD1.0-CI 50 μg E (n = 10) pVKD1.0-NP 50 μg pVKD1.0-CI-LMNB 100 μg LMNB-I13/CFA 10 μg LMNB-C10/IFA 10 μg pVKD1.0-CI 50 μg F (n = 10) pVKD1.0-NP 50 μg pVKD1.0-CI-LMNB 100 μg LMNB-C10/CFA  5 μg LMNB-C10/IFA  5 μg pVKD1.0-CI 50 μg LMNB-I13/CFA  5 μg LMNB-I13/IFA  5 μg

The tumor growth of immunized mice in each group is shown in FIG. 27. Among them, all the mice in the control group (group A) developed tumors on the 14th day after the tumor challenge (i.e. after the tumor innoculation), and the tumors grew rapidly. The tumor growth of mice in each immunization group lagged behind that in the control group, wherein the mice in the group boosted with LMNB-I13 (group D) and the nice in the group boosted with a mixture of LMNB-I13 and LMNB-C10 (group E) had the slowest tumor growth, so these two groups of vaccines had the best effects.

In addition, an analysis of tumor-free survival was performed for the mice, and the results are shown in FIG. 28. The median tumor-free survival (TFS) of the mice in the control group A was 14 days. The tumor-free survival of the mice in each vaccine immunized group was significantly higher than that in the control group, indicating that all vaccines could increase the tumor-free survival of immunized mice. Among them, group D with the I13 epitope fusion peptide, and group E and F with the I13 and C10 epitope fusion peptide had the best effects, and the tumor-free survival of mice was doubled at the most. In the vaccine group with the I13 epitope fusion peptide (group D), the tumor-free survival was significantly increased by about 40% compared to the conventional vaccine group (group B), showing that a load of 13 Th epitopes of Flu virus or 10 Th epitopes of CMV could significantly improve the protection effect of tumor vaccine against tumor.

Finally, an analysis of mouse overall survival was also performed and the results are shown in FIG. 29. Among them, the median overall survival (OS) of mice in control group A was 35 days. The overall survival of mice in each vaccine immunized group was significantly higher than that in the control group, indicating that all vaccines could increase the survival of mice after immunization. Among them, group D with I13 epitope fusion peptide and groups E and F with I13 and C10 epitope fusion peptides had the best effects, and the overall survival rate was increased by 83%. Compared with the conventional vaccine group (group B), the vaccine group with the I13 epitope fusion peptide (groups D and group F) significantly increased the tumor-free survival by 28% at the most, indicating that a load of thirteen (13) Flu virus Th epitopes or ten (10) CMV Th epitopes could greatly improve the tumor protection effect of tumor vaccine.

Example 14 Tumor Treatment Experiment

The vaccines involved are shown in Example 9. Thirty (30) 6-8 weeks old female BAL B/c mice were purchased from the Laboratory Animal Center of Suzhou University and raised in the SPF animal house of the Laboratory Animal Center of Suzhou University. The experimental animal grouping and vaccination schemes are shown in Table 25. All DNA vaccines were injected into the tibialis anterior muscle of the calf at 100 μg/animal. All protein vaccines were fully emulsified with complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA) and injected subcutaneously into the back at 10 μg/animal. Two weeks after the last immunization, the mice were inoculated subcutaneously with the cell line transfected stably by the tumor cells 4T1-hNY-ESO-1 (provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park), at a dose of 1×10⁵ cells/mouse, and the corresponding mice were inoculated subcutaneously with the protein vaccine on day 1, 8 and 15 after the tumor cell inoculation, respectively. The tumor growth was continuously observed and measured after the inoculation. The tumor volume was calculated according to the following equation: tumor volume (mm³)=length×width²/2. The mice were sacrificed when the tumor volume exceeded 2000 mm³.

TABLE 25 Grouping and immunization schemes Week 0, 4, 8 Week 10 Week 11, 12 Grouping Vaccine Dose Vaccine Dose Vaccines Dose A (n = 10) pVKD1.0-NP 100 μg pVKD1.0 100 μg VP1/CFA 10 μg B (n = 10) pVKD1.0-NP 100 μg LMNB/CFA  10 μg LMNB/IFA 10 μg C (n = 10) pVKD1.0-NP 100 μg LMNB-I13/CFA  10 μg LMNB-I13/IFA 10 μg

The tumor growth of immunized mice in each group is shown in FIG. 30. Among them, all the mice in the control group (group A) developed tumors on the 14th day after the tumor challenge (i.e. after the tumor innoculation), and the tumors grew rapidly. The mice in the LMNB-I13 protein vaccine treated group (group C) had the slowest tumor growth compared to the untreated control group (group A). Furthermore, the tumor size of mice in the LMNB-I13 protein vaccine treated group was significantly smaller than that in the control group (group A) on day 22 after the tumor challenge, and there was still a significant difference in tumor size between the two groups until day 30. By day 35, the tumor growth of mice began to accelerate in group C, which is possibly associated with the cease of vaccination with the LMNB-I13 protein vaccine. The results indicated that the LMNB-I13 protein vaccine could inhibit tumor growth in mice.

Example 15 Tumor Treatment Experiment

The vaccines involved are shown in Example 9. Thirty (30) 6-8 weeks old female BAL B/c mice were purchased from the Laboratory Animal Center of Suzhou University and raised in the SPF animal house of the Laboratory Animal Center of Suzhou University. The experimental animal grouping and vaccination schemes are shown in Table 26. All DNA vaccines were injected into the tibialis anterior muscle of the calf at 100 μg/animal. All protein vaccines were fully emulsified with complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA) and injected subcutaneously into the back at 10 μg/animal. Two weeks after the last immunization, the mice were inoculated subcutaneously with the cell line transfected stably by the tumor cells CT26-hLAGE-1 (provided by Vacdiagn Biotechnology Co., Ltd., Suzhou Industrial Park), at an inoculation dose of 1×10⁵ cells/mouse, and the corresponding mice were inoculated subcutaneously with the protein vaccine on day 1, 8 and 15 after the tumor cell inoculation, respectively. The tumor growth was continuously observed and measured after the inoculation. The tumor volume was calculated according to the following equation: tumor volume (mm³)=length×width²/2. The mice were sacrificed when the tumor volume exceeded 2000 mm³.

TABLE 26 Grouping and immunization schemes Week 0, 4, 8 Week 10 Week 11, 12 Grouping Vaccine Dose Vaccine Dose Vaccine Dose A (n = 10) pVKD1.0-NP 100 μg pVKD1.0 100 μg VP1/CFA 10 μg B (n = 10) pVKD1.0-NP 100 μg LMNB/CFA  10 μg LMNB/IFA 10 μg C (n = 10) pVKD1.0-NP 100 μg LMNB-I13/CFA  10 μg LMNB-I13/IFA 10 μg

The tumor growth of immunized mice in each group is shown in FIG. 31. Due to the failure of tumor innoculation of some mice in the untreated control group (group A) after the tumor challenge (i.e. after the tumor innoculation), such mice were not included for the analysis, and the parallel controlled vaccine group (group B) and the LMNB-I13 treated group (group C) were compared. Compared with group B, the tumor growth of mice in group C was slower, and the tumor size of mice in the LMNB-I13 protein vaccine treatment group was significantly smaller than that in parallel controlled vaccine group (group B) on day 22 after the tumor challenge. There was still a significant difference in tumor size between the two groups until day 30. Similarly, the increased tumor growth of mice in group C was also observed at a later stage in the CT26 mouse model, which is possibly associated with the cease of vaccination with the LMNB-I13 protein vaccine. These results indicated that the LMNB-I13 protein vaccine could inhibit tumor growth in mice. 

The invention claimed is:
 1. A fusion peptide of CD4 helper T cell epitopes comprising a cytomegalovirus (CMV) epitope and/or an influenza virus epitope, wherein there are at least 5 CMV epitopes and/or at least 8 influenza virus epitopes, wherein the at least 5 CMV epitopes comprise pp65-11 (SEQ ID NO. 1), pp65-71 (SEQ ID NO. 2), pp65-92 (SEQ ID NO. 3), pp65-123 (SEQ ID NO. 4), and pp65-128 (SEQ ID NO. 5), and wherein the at least 8 influenza epitopes comprise HA203 (SEQ ID NO. 11), NP438 (SEQ ID NO. 12), NS1-84 (SEQ ID NO. 13), M1-181 (SEQ ID NO. 14), HA375 (SEQ ID NO. 15), NP24 (SEQ ID NO. 16), NP95 (SEQ ID NO. 17), and NP221 (SEQ ID NO. 18).
 2. The epitope fusion peptide of claim 1, further comprising one or more of CMV epitopes selected from those shown in SEQ ID NOs: 6-10, and/or one or more of influenza virus epitopes selected from those shown in SEQ ID NOs: 19-23.
 3. The epitope fusion peptide of claim 1, further consisting of one or more of CMV epitopes selected from those shown in SEQ ID NOs: 6-10, and/or one or more of influenza virus epitopes selected from those shown in SEQ ID NOs: 19-23.
 4. A fusion protein comprising an epitope fusion peptide of claim 1, and a target immunogen.
 5. The fusion protein of claim 4, wherein the target immunogen is selected from a peptide, an antigen, a hapten, a carbohydrate, a protein, a nucleic acid, an allergen, a virus or a part of a virus, a bacterium, a parasite or other whole microorganism.
 6. A polynucleotide encoding the epitope fusion peptide of claim
 1. 7. An immunogenic composition comprising a prophylactically or therapeutically effective amount of the epitope fusion peptide of claim 1, and a pharmaceutically acceptable carrier.
 8. A method for increasing the immunogenicity of a target immunogen using the epitope fusion peptide of claim 1, comprising fusing a CD4 helper T cell epitope having a stronger immune response in a vaccine subject or population with a target immunogen to form a fusion protein.
 9. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the fusion peptide of claim 1 with a pharmaceutically acceptable carrier.
 10. The epitope fusion peptide of claim 3, wherein the epitope fusion peptide consists of 5 or 10 CMV epitopes, and/or 8 or 13 influenza virus epitopes.
 11. The epitope fusion peptide of claim 10, wherein the epitope fusion peptide is shown in SEQ ID NO: 34 or
 44. 12. The epitope fusion peptide of claim 3, wherein the epitope fusion peptide consists of 13 influenza virus epitopes.
 13. The epitope fusion peptide of claim 12, wherein the epitope fusion peptide is shown in SEQ ID NO:
 48. 14. The fusion protein of claim 5, wherein the antigen is a tumor antigen or an infection-related antigen.
 15. The fusion protein of claim 14, wherein the tumor antigen is one or more tumor antigens selected from lung cancer antigen, testicular cancer antigen, melanoma antigen, liver cancer antigen, breast cancer antigen or prostate cancer antigen.
 16. The fusion protein of claim 14, wherein the tumor antigen is one or more tumor antigens selected from LAGE antigen, MAGE antigen or NY-ESO-1 antigen.
 17. The fusion protein of claim 16, wherein the LAGE antigen is LAGE-1, and the MAGE antigen is MAGE-A3.
 18. The fusion protein of claim 17, wherein the amino acid sequence of LAGE-1 is shown in SEQ ID NO: 24, the amino acid sequence of MAGE-A3 is shown in SEQ ID NO: 25, and the amino acid sequence of NY-ESO-1 is shown in SEQ ID NO:
 26. 19. The fusion protein of claim 14, wherein the infection-related antigen is one or more infection-related antigens selected from an HIV antigen, an influenza virus antigen or an HBV antigen.
 20. The fusion protein of claim 5, wherein the fusion protein is shown in one of SEQ ID NOs: 55-58.
 21. A polynucleotide encoding the fusion protein of claim
 4. 22. An immunogenic composition comprising a prophylactically or therapeutically effective amount of the fusion protein of claim 4 and a pharmaceutically acceptable carrier.
 23. An immunogenic composition comprising a prophylactically or therapeutically effective amount of the polynucleotide of claim 6 and a pharmaceutically acceptable carrier.
 24. An immunogenic composition comprising a prophylactically or therapeutically effective amount of the polynucleotide of claim 21 and a pharmaceutically acceptable carrier.
 25. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the fusion peptide of claim 4 with a pharmaceutically acceptable carrier.
 26. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the polynucleotide of claim 6 with a pharmaceutically acceptable carrier.
 27. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the polynucleotide of claim 21 with a pharmaceutically acceptable carrier.
 28. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the immunogenic composition of claim 7 with a pharmaceutically acceptable carrier.
 29. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the immunogenic composition of claim 22 with a pharmaceutically acceptable carrier.
 30. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the immunogenic composition of claim 23 with a pharmaceutically acceptable carrier.
 31. A method for the preparation of a medicament or a vaccine for increasing the immunogenicity of a target immunogen, comprising formulating the immunogenic composition of claim 24 with a pharmaceutically acceptable carrier. 